The invention relates to an air inlet for a vehicle, to the use of an air inlet for a vehicle, as well as to a vehicle comprising at least one air inlet.
Various systems in vehicles depend on being supplied with, or cooled with, external air. For example, vehicles are equipped with NACA air inlets in order to supply air conditioning equipment, ventilation systems and cooling systems as effectively as possible with external air. The particular shape of the NACA inlet, also referred to as a NACA duct or NACA scoop, was developed with the aim in aircraft in flight to guide flow that is as high in energy as possible from outside the aerodynamic boundary layer into the inlet, while at the same time increasing the aerodynamic drag of the aircraft itself as little as possible. The use of NACA inlets is very common, not only in aircraft engineering, but for example also in motor vehicles, fast trains and the like.
A NACA inlet is characterised by its curved divergent opening contour in the outer skin of the vehicle; by the bottom element that extends into the interior of the vehicle, which bottom element is usually designed as a ramp with a relatively flat angle to the outer skin; by the sharp-edged transition between the sidewalls of the bottom element and the outer skin; as well as by the so-called lip or border edge at the beginning of the connected air guide channel.
The effect of a NACA inlet is based on the fact that, for example in an aircraft in flight, at the edges of the opening contour counter-rotating vortices are generated that lead fast high-energy air from outside the aerodynamic boundary layer into the air guide channel. For example for cooling purposes, many vehicle systems draw in outside air through their NACA inlets also in stationary operation, i.e. in the case of aircraft specifically when they are situated on the ground. In stationary operation, drawing in air by way of all the opening edges of the NACA inlet results in a clearly noticeable noise, the volume of which with the usual shape of the inlet can only be reduced by increasing the cross-sectional area and thus by reducing the resulting air speed. However, in many vehicles, and in particular in aircraft, due to the very confined installation space, noise reduction can often not be achieved by increasing the cross-sectional area.